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Answer:
"Any element with a high electronegativity and an element with a single valence electron would react very easily on contact with each other."
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"Why?"
For instance, fluorine is the most reactive non-metal element on the periodic table. Due to it's small size, as well as it's strong electronegativity, fluorine has a strong tendency to accept electrons from other atoms and ions. But when Fluorine comes in contact with Hydrogen (a single valence electron element), for instance, it immediately reacts, resulting in an explosion.
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Hope this helps!